Poster: Oxidative stress
Abs #
75: Chilling tolerance processes are activated by glycine betaine in Arabidopsis
Glycine betaine (GB) application to plants or overproduction of GB in transgenics leads to increased tolerance to the damaging effects of stresses caused by drought, frost, salt and chilling. In Arabidopsis, GB activates expression of several stress-related genes. Using microarray technology, we have identified several of these genes, finding that many of them are involved in reactive oxygen species (ROS) metabolism. Among ROS-related genes affected by GB are monodehydroascorbate reductase, NADPH oxidase, glutathione S-transferase and peroxidase. Two GB-activated genes involved in stress tolerance (GLYB genes) have been investigated in Arabidopsis knockout mutants. One of the genes (GLYB1) codes for a bZIP transcription factor while the other gene (GLYB2) codes for a Rab protein involved in vesicles trafficking. Both knockout mutants accumulate superoxide at 4 C in the light. Based on these and related studies, we have developed a cellular model for chilling tolerance in Arabidopsis as follows: at low, non-freezing temperatures, light energy is converted in the chloroplast to strong reductant which is used to reduce oxygen to superoxide and for further ROS production. Substantial amounts of ROS are detoxified in the cell wall by peroxidases made on the ER, then transported through the Golgi system to the cell wall via vesicle trafficking to the plasma membrane which depends on Rab proteins coded by genes such as GLYB2.
